Magnetic core structures



Sept. 28, 1965 A, R. CORNELL 3,209,294

MAGNETIC CORE STRUCTURES Fild OG'I. 25, 1962 v TTORNEY United States Patent O 3,209,294 MAGNETIC CORE STRUCTURES Archie R. Cornell, Avon Lake, Ohio, assigner to Westinghouse' Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 23, 1962, Ser. No. 232,499 3 Claims. (Cl. 336-134) This invention relates to magnetic core structures, and more particularly to magnetic core structures such as those used in reactor and transformer coil and core assemblies, designed to have one of more air gaps which c-an be readily adjusted to vary the reactance of the assembled unit.

In recent years, ferrite cores, and especially ferrite cupcores have ben increasingly utilized in such reactor and transformer devices. Due to manufacturing processes the tolerances of the magnetic properties of ferrites are not as close as commercially desirable, sometimes having a variance of as much as Therefore, some means are necessary to compensate for this variance during the final assembly of the coil and core into the completed unit to be used as a reactor or transformer or some other magnetic core device.

Accordingly, it is an object of this invention to provide a new and improved magnetic core structure.

It is a further object of this invention to provide an improved powdered and/or ferrite core structure which, when combined with a coil winding, can be readily adjusted to vary the reactance of the coil and core unit.

It is a general object of this invention to provide methods and means of obtaining adjustable air gaps in powdered and/or ferrite cores during the assembly thereof into coil and core structures.

Briefly, the present invention accomplished the above cited objects by providing a core composed of two or more parts, one or more of which is relatively movable with respect to the others to variably adjust one or more air gaps within the core during the assembly process just prior to binding the core members and coil together into a rigid unit in a predetermined adjusted relationship.

Further objects, features and advantages of the invention will become apparent as the following description proceeds, and features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

The accompanying drawings show the various modifications of the invention as either generally planar or cupped core structures. However, the invention in its various applications is intended for use with either core structure, and such figures are intended to apply equally to either type core structure since the invention relates primarily to the adjustability features 0f the core structures and not to specific overall configurations. For ease of explanation, certain of the drawings will refer to planar configurations while others will refer to cupped configurations but it is intended that the drawings also be descriptive of sections through a corresponding cup-core structure and of planviews of corresponding planar configurations, respectively. Any refinement which will be applicable to the one type core more so than the other will be pointed out with greater detail hereinafter.

FIGURE 1 is a plan view of a core structure employing additional relatively stationary members;

FIG. 2 is `a plan view of another core arrangement of' the invention consisting of two E-section core members and one I-section core member and arranged to form adjustably bridged gaps as well as additional air gaps;

FIG. 3 depicts a plan view of another core arrangement of the invention utilizing a Tsection member slidable with respect to and within an E-section member;

FIG. 4 is a plan View of an alternative form of the core arrangement of FIG. 3;

FIG. 5 is a plan view of still another core structure with screw-threaded center-legs providing adjustable air gaps;

FIG. 6 is a longitudinally sectioned View taken generally along reference line VI-VI of FIG. 7 and showing a core structure arranged in accord with the invention and composed of two cup-cores in facing relationship, one of which has a movable central core leg;

FIG. 7 is a cross-sectional view of the core structure taken along line VII-VII of FIG. 6;

FIG. 8 is a longitudinally sectioned view of another form of a cup-core structure according to the invention;

Referring now to the drawings, the core structures depicted therein are generally of the type which have a central core leg having one or more coil windings located thereon while the remaining portion of the core for-ms a closed magnetic circuit enclosing the coil windings.

It is to be understood that the cores shown in the accompanying drawings can be of solid, laminated, or powdered ferrite construction and is not to be limited to any one type of construction although certain structures may be more readily adaptable to a specific type construction.

The core arrangement of the invention shown in FIG. 1 includes two bar members 28 and two T-section members 30 interposed between and slidable within the bar members to effect adjustment of the air gap 32 after the assembly of the coil and core unit. If a cylindrical core configuration is desired, the two bar members 28 would represent a cylindrical sleeve which would have slidably interposed therein one or both of the members 30 which would have a circular flange section 31 of practically the same outer diameter `as the inner diameter of the cylindrical sleeve 28. A central stud section or core leg 34 is .affixed thereto upon which are located suitable core windings positioned within the annular chamber 36 formed by the inner wall of sleeve 28 and the outer walls of legs 34. Alternatively, one or both of the members 30 could be threaded about the periphery of the flange section 31 with a corresponding threaded portion of the sleeve 28 at the junction (as shown on one of the members 30) whereby adjustment of the air gap 32 could be effected by rotation. A slot (not shown) could be formed in the flange 31 for insertion of a tool for rotating the member 30. If' a powdered or magnetic ferrite material is used in the core, the threads on both these sleeves 38 and the flange 31 can be formed while these parts are made in the die and no machining or grinding of the threads is required. After the desired adjustment is made, the parts can be cemented together to maintain the adjustment.

As shown in FIG. 2 another form of the invention comprises two facing Ecores 40 which are notched in their outer legs as denoted by the reference characters 41 and an I-core member 42 interposed between the facing E-core members 4t) to mate with the notches in close fitting relationship to permit relative movement 4of the parts for adjustment of the air gaps 44 located between the centrally extending legs 48 of lthe E-cores 40 and the longitudinal walls of the I-core 42 after insertion of coil windings into the winding receiving openings 46. By placing spacers which can be made of nonmagnetic material in the gaps 43 formed at the junction of the I-core 42 with the E-cores 40, it is possible to preserve the adjustment imparted to the air gaps 44 within the length of the notches 41 to affect the reactance of the assembled unit. The fixation of the adjustment is completed by applying clamping means (not shown) to the upright portions 45 of the E-cores 40. This arrangement can be modified by utilizing a single E-core member 40 and a U-core member (not shown) which would engage the E-core member 40 at its notched outer legs 41 ina manner similar to that of the I-core 42.

FIG. 3 shows a core construction similar to FIG. 2, wherein an E-core 50 (or a cupped-core) having a shorter -centrally extending leg 52 and a T-core 54 with a truncated centrally exten-ding leg 58 slidably interposed between the outer legs of the E-core 50. The E-core leg 52 and the truncated leg 58 are coaxial and form an air gap 56 between the ends thereof which may be varied by sliding the T-core 54 after the insertion Vof the coil into the coil receiving opening 60. The unit can then be bound together in a known fashion to maintain the adjustment of the air gap 56. Alternatively, if a cupped conliguration be employed, the iianged portion S and the .inner surface of the cylindrical barrel of the cup-core can be matingly threaded for adjust-ment, in the manner described above in connection with FIG. 2.

The core structure `of FIG. 4 is similar in operation to that of FIG. 2 whereby the E-core 62 has a shorter centrally extending leg 64 and has outer legs 66 notched on the internal surface thereof and a bar core 68 is slidably interposed therein to alter the length of the air gap 70 which is formed between the leg 64 and the adjacent surface of the bar core 68. Spacers (not shown) of predetermined thickness may be inserted in the space 72 formed by the notched outer legs 66 and the bar core 68 after a coil is located on leg 64 just prior .to insertion of the bar core 68. In the case of a cupped configuration, the bar core 68 represents a disk configuration, and the aforesaid spacers must, of course, be added prior to insertion of the disk-core.

By utilizing a cylindrical core or cup-core configuration for the core structures, the core structures of FIGS. 2 and 4 can `also be threaded in a manner similar to that described in connection with FIGS. l or 3 whereby adjustment of the respective air gaps is effected by rotation.

It is also seen that the peripheral gaps 43 and 72 of FIGS. 2 and 4, respectively, form adjustably bridged gaps in the corresponding core structures, which bridged gaps are adjusted simultaneously and in .the same manner as the respectively related air gaps 44 and 70 to aid in varying the reactance of the respective core structures.

The core structure lof FIG. 5 utilizes two U-shaped cores 74 formed from ferrite or other suitable magnetic material and positioned so that their open ends are facing and their respective leg portions are aligned. A bar 76 is interposed between the facing cores 74 and the unit is bound together so that the respective legs of the U-shaped cores 74 abut the juxtaposed face of the bar 76. The base of each core 74 is provided with a centrally located threaded laperture 78 through which is inserted a correspondingly threaded central core leg 80 which forms an air gap 82 between the end thereof and the adjacent surface tof the disk 76. Thus, with one or more coils positioned in the -coil winding receiving openings 86, the air gaps 82 can be .adjusted to vary the reactance by insertion of a screwdriver or other device into slot 84 provided in the external end of the leg 80. This arrangement obviously can be modified if desired by eliminating one core 74 and its corresponding leg 80.

It is, of course, obvious that the cores 74 can represent sections of cup cores and the member 76 interposed therebetween can represent the cross-section of a disk juxtaposed with the annular rims of the cup-cores 76 without departing fr-om .the spirit of the invention. The adjustability feature of .the core legs S0 would remain functionally the same.

The core construction illustrated in FIG. 6 shows an E- section, ferrite cup-core 88 with its opening facing the opening of a second cup-core 90 which has a movable center core leg 92. The leg 92 is inserted through a centrally located aperture inthe base of the core 90, the aperture having generally the same cross-section as the leg 92. The leg 92 desirably is coaxial with the centrally extending leg 94 of the E-core 88 and bolt receiving holes extends through the legs. A bolt 96 whichdesirably is made of a nonmagnetic material such as brass is inserted through the movable core section 92 and the center leg 94 of the E-section cup-core 88 for purposes of holding the unit together and adjusting the nonmagnetic gap 98 by varying the pressure applied to .a metallic or rigid washer 100 which may be secured to the leg 92 and a suitably shaped disk 102 which is fabricated from a compressible or resilient material such as rubber. The washer 100 and the disk 102 are interposed between the head of the bolt 96 and the base of the cup-core 90 adjacent the aforementioned aperture. The nonmagnetic gap 98 can also contain a disk or washer 99 of similar nonmagnetic compressible or resilient material. Alternatively either or both of the disks 99 and 102 can be formed from suitably shaped nonmagnetic conical or helical springs, or other resilient members. This arrangement permits the movement of the core leg 92 through the central aperture of the cup-core 90 and relative to the stationary center leg 94 of the cupcore 88 to provide variation in the width of the nonmagnetic gap 98 Iin order to obtain proper reactance adjustment. Thus, the nonmagnetic gap 98 is varied by turning .the brass bolt which Varyingly compresses or deforms the members 102 and/ or the .similar washer 99. It is to be understood that, in certain applications either one of the deformable members 102 or 99 can be eliminated, as long as the remaining member 102 or 99 offers sufficient biasing force against the bolt 96 to maintain the adjustment.

FIG. 7 shows the cross-sectional configuration of the core construction of FIG. 6 and depicts the movable leg 92 as being square in cross-section but it need not be limited to that configuration, since it can also be circular in cross-section, for example, or any other suitable configuration depending upon the intended application and desired manufacturing technique.

A modified form of the core structure shown in FIG. 6 is illustrated in FIG. 8 and comprises a cup-core 104 and an end disk 106 positioned in abutting relationship with the annular rim of the cup-core 104. The cup-core 104 has a centrally located aperture in its base for insertion of a movable central core leg 108 which has a bolt receiving hole extending the length thereof. Another bolt receiving hole is located in the end disk 106 and is coaxial with the hole in the leg 108. A bolt 110 which can be fabricated as pointed out in connection with the bolt 96 of FIGS. 6 and 7 is inserted through the bolt receiving hole in the leg 108 and the end disk 106 for purposes of adjustment and binding the unit together. A rigid washer 112 and a compressible or resilient washer or member 114 are interposed between the head of the bolt 110 and the base of the cup-core 104, and another compressible or resilient washer or member 116 can be inserted between the end of the leg 108 and the adjacent face of the disk 106. The members 114 and 116 can be fabricated as pointed out previously in describing the resilient members 99 and 102 of FIGS. 6 and 7. Thus, after insertion of a coil winding into the winding receiving opening 118 the bolt 110 can be tightened to exert pressure against the resilient members 116 and 114 to alter the width of the nonmagnetic gap at 116 and thereby vary the reactance of the completed unit. Also, as pointed out lrelative to FIGS. 6 and 7, one of the resilient members 114 or 116 can be eliminated in certain applications of this modification of the invention.

It can be readily seen from the foregoing description that the core structures as illustrated contain a completely closed magnetic circuit in its outer periphery while still providing an air gap within the unit to vary the reactance by external means or manipulation after the coil and core are assembled.

It is to be understood that the core arrangements of FIGS. 6 and 8 can be of planar contiguration insofar as at least the cup-cores 88, 90 and 104 are concerned, as denoted by the dashed outline of FIG. 8.

While there have been shown and described what are at present considered to be the preferred embodiments of the invention, modifications thereto will readily appear to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangements shown and described, and it is intended to cover in the appended claims all such modifications that fall within the true spirit and scope of the invention.

I claim as my invention:

1. In a magnetic core structure having an adjustable width air gap, the combination comprising:

(a) a main core member having a cros ssection including at least as a part thereof a U-shaped configuration having a bight portion, said main core member having an aperture provided in the bight portion of said U-shaped configuration;

(b) a removable magnetic closure member abuttingly engaging the free ends of said U-shaped configuration;

(c) a movable core leg extending into said main core member from said aperture, the outer end of said core leg movably fitting within said aperture and the inner end of said core leg extending into said main core member and disposed proximate said closure member forming an adjustable Width air gap therebetween;

(d) holding means affixed to the outer end of said core leg engaging said main core member adjacent said aperture to hold said core leg to said main core member; and

(e) adjustable securing means positioned within said main core member and bridging said gap for adjusting the width thereof and for securing said closure means to said core leg, said core leg binding said core structure together by means of said holding means and said securing means affixed to either end of said core leg.

2. The magnetic core structure as specified in claim 1 wherein a first resilient means is provided within said adjustable width air gap retaining the adjustment thereof, said first resilient means traversed by said adjustable securing means, and a second resilient means disposed between said holding means and said main core member which allows relative motion therebetween while said holding means holds said core leg to said main core member.

3. The magnetic core structure as specified in claim 1 wherein said main core member is a cup-shaped member having a generally U-shaped cross section and having an aperture provided in the bight portion thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,476,854 7/49 Friend 336-134 X 2,674,721 4/54 Jackson et al. 336-134 2,786,983 3/57 Hill 336-l34 X 2,879,489 3/59 Mitchell 336-134 X JOHN F. BURNS, Primary Examiner. LARAMIE E. ASKIN, Examiner. 

1. IN A MAGNETIC CORE STRUCTURE HAVING AN ADJUSTABLE WIDTH AIR GAP, THE COMBINATION COMPRISING: (A) A MAIN CORE MEMBER HAVING A CORS SECTION INCLUDING AT LEAST AS A PART THEREOF A U-SHAPED CONIFIGURATION HAVING A BIGHT PORTION, SAID MAIN CORE MEMBER HAVING AN APERTURE PROVIDED IN THE BIGHT PORTION OF SAID U-SHAPED CONFIGURATION; (B) A REMOVABLE MAGNETIC CLOSURE MEMBER ABUTTINGLY ENGAGING THE FREE ENDS OF SAID U-SHAPED CONFIGURATION; (C) A MOVABLE CORE LEG EXTENDING INTO SAID MAIN CORE MEMBER FROM SAID APERTURE, THEOUTE END OF SAID CORE LEG MOVABLY FITTING WITHIN SAID APERTURE AND THE INNER END OF SAID CORE LEG EXTENING INTO SAID MAIN CORE MEMBER AND DISPOSED PROXIMATE SAID CLOSURE MEMBER FORMING AN ADJUSTABLE WIDTH AIR GAP THEREBETWEEN; (D) HOLDING MEANS AFFIXED TO THE OUTER END OF SAID CORE LEG ENGAGING SAID MAIN CORE MEMBER ADJACENT SAID APERTURE TO HOLD SAID CORE LEG TO SAID MAIN CORE MEMBER; AND (E) ADJUSTABLE SECURING MEANS POSITIONED WITHIN SAID MAIN CORE MEMBER AND BRIDGING SAID GAP FOR ADJUSTING THE WIDTH THEREOF AND FOR SECURING SAID CLOSURE MEANS TO SAID CORE LEG, SAID CORE LEG BINDING SAID CORE STRUCTURE TOGETHER BY MEANS OF SAID HOLDING MEANS AND SAID SECURING MEANS AFFIXED TO EITHER END OF SAID CORE LEG. 